Ineed some reasons besides pregnancy and std's to not become sexually active?

Not only do you get stds you get STI's aswell, and you can get HIV

Can you explain it well?

Smoking damages the respiratory system by inhalation of a foreign substance, that is absorbed and residue is left behind on our lungs sponge like substance. the gas that is inhaled also increase your blood pressure and dilates your blood vessels. also the process of inhaling and exhaling the smoke it causes irritation to the throat and mouth. smoking can cause lung cancer and other respiratory and circulatory diseases.